Display screen or portion thereof with a graphical user interface having a transitional icon



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface having a transitional icon, showing our new design and, in particular, showing a first image thereof.

FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface having a transitional icon, showing our new design, and in particular, showing a second image thereof.

FIG. 3 is a front view of a display screen or portion thereof with a graphical user interface having a transitional icon, showing our new design, and in particular, showing a third image thereof; and,

FIG. 4 is a front view of the display screen or portion thereof with a graphical user interface having a transitional icon, showing our new design, and in particular, showing a fourth image thereof.

The broken lines illustrate an electronic device, which is the environment of the design, and which forms no part of the claimed design. The remaining broken lines illustrate portions of the display screen and portions of the graphical user interface that form no part of the claimed design.

The appearance of the graphical user interface with the transitional icon sequentially transitions among the images shown in FIGS. 1-4. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface having a transitional icon, as shown and described. 